At the close of today’s trading, Apple’s stock price was $522.41 a share. That makes the Cupertino, California-based company worth about $487 billion — more than any other company in the world. But long before the iPad, iPhone, and iPod — before even the Macintosh computer — Apple was a lowly Silicon Valley startup, much like so many are today. And at that time, the company consisted of three men. Two of them we know quite well: Steve Wozniak, and (of course) Steve Jobs. The third man, Ronald G. Wayne, is far less famous. That’s because he left what would become the world’s most valuable company after only 12 days on the job.

In retrospect, doing such a thing sounds like some sort of nightmare, one in which you accidentally toss a winning lottery ticket in the trash, or disregard a priceless relic in your attic as a hunk of worthless old junk. And over the years Wayne’s early departure has been characterized in the press as just that. But this week, the man came out of the shadows of could-have-been history to give his side of the story.

“I didn’t separate myself from Apple because of any lack of enthusiasm for the concept of computer products,” writes Wayne in a Facebook post (of all things). “Aside from any immediate apprehension in regard to financial risks, I left because I didn’t feel that this new enterprise would be the working environment that I saw for myself, essentially for the rest of my days. I had every belief I would be successful but I didn’t know when, what I’d have to give up or sacrifice to get there, or how long it would take to achieve that success.”

In short, explains Wayne, the reason he left Apple was because it was simply not his passion. “Steve and Steve had their project,” he writes. “They wanted to change the world in their way. I wanted to change the world in my own.”

Wayne also counters the conclusion that he lost out on a fortune — or, at least, a fortune in the billions of dollars. As a founding partner, Wayne owned 10 percent of Apple when he left the company, for which he received about $9,600 (in today’s dollars). Had he kept that 10 percent, he would be worth more than $48.7 billion today. Of course, holding onto that much stock for 36 years is a highly unlikely scenario, especially given Apple’s tumultuous past.

“Apple went through a lot of hard times and many thought Apple would simply go out of business at various times in its maturity,” writes Wayne. “I perhaps lost tens of millions of dollars. And quite honestly, between just you and me, it was character building.

“If I had known it would make 300 people millionaires in only four years, I would have stayed those four years. And then I still would have walked away.”

In the end, Wayne says he has no regrets. The apparent reason for posting about his short time with Apple now appears to be because of the release of his book, Insolence of Office, which Wayne proudly says is, “in itself, enough to justify [his] existence on this planet.”

If you’re interested in reading Insolence of Office, you can get it in paperback from Amazon (here), for Kindle (here), or (ironically), from iTunes (here).